Fundamentals of thermoplastic sandwich structure fabrication using laser-based in-situ thermoplastic Automated Fiber Placement. (TheSaLab)

碳纤维增强塑料（CFRP）结构由于其高比强度而具有巨大的轻量化潜力。近年来，趋势已经从热固性材料转向热塑性材料，以便利用可回收性的优点以及通过基体的局部熔融将两个组分连接起来。通过夹层结构实现了特别好的机械性能与重量的比率。使用常规工艺制造热塑性夹层结构目前限于平坦夹层结构。用于生产三维结构的一些方法需要高度复杂的模具以及多步骤制造工艺，并且还限于要限定的单个形状。另一方面，热塑性自动纤维铺放（TAFP）提供了一种灵活的纤维复合材料制造工艺。对于使用类似半成品的工艺，已经有了对工艺的全面了解。然而，有一个缺乏知识的机制和各向异性磁带上各向同性泡沫结构的沉积过程中的光-热-机械相互作用的特性。初步研究表明，在TAFP工艺条件下，原则上可以在沉积带和泡沫芯之间形成内聚粘合。然而，如果选择不合适的工艺参数，则会发生泡沫结构的局部塌陷或两个连接伙伴的不充分的内聚结合。因此，本项目的目的是发展的光学和热机械的相互作用之间的关系，在加热和连接区的碳纤维增强的热塑性带的沉积过程中，热塑性泡沫芯使用激光TAFP的基本理解。为此目的，在第一步骤中，研究激光辐射与泡沫材料和预浸带的光学相互作用，并且根据激光设置以基于模型的方式确定由两个接合伙伴的反射、吸收和透射特性引起的加热区中的功率分布。此外，泡沫和固结辊的行为在工艺参数下进行机械表征，并转移到材料模型中。调查的结果将结合起来，并在热机械过程模型中进行验证。通过耦合热机械过程模型与粘结强度模型，将探讨工艺参数对沉积带层和泡沫芯之间的粘结质量的影响。通过产生一个基本的理解，单独弯曲的热塑性夹层结构，使用基于激光的TAFP制造的基础。

Structures made of carbon fiber reinforced plastic (CFRP) offer enormous lightweight potential due to their high specific strengths. In recent years, the trend has been moving from thermoset to thermoplastic materials in order to exploit the advantages of recyclability as well as the joining of two components by local melting of the matrix. A particularly good ratio of mechanical properties to weight is achieved by sandwich structures. The manufacture of thermoplastic sandwich structures using conventional processes is currently limited to flat sandwich structures. A few approaches for the production of three-dimensional structures require highly complex molds as well as multi-step manufacturing processes and are also limited to a single shape to be defined. Thermoplastic Automated Fiber Placement (TAFP), on the other hand, offers a flexible fiber composite manufacturing process. A comprehensive understanding of the process already exists for processes in which similar semi-finished products are used. However, there is a lack of knowledge about the mechanisms and the characteristics of the optical-thermal-mechanical interactions during the deposition of anisotropic tapes on isotropic foam structures. Preliminary investigations have shown that the formation of a cohesive bond between deposited tapes and foam core is possible in principle under TAFP process conditions. However, if unsuitable process parameters are selected, local collapse of the foam structure or insufficient cohesive bonding of the two joining partners occurs. The aim of this project is therefore to develop a fundamental understanding of the relationships between the optical and thermomechanical interactions in the heating and joining zones during the deposition of carbon fiber reinforced thermoplastic tapes on thermoplastic foam cores using laser-based TAFP. For this purpose, in a first step, the optical interaction of the laser radiation with the foam material and the prepreg tapes is investigated and the power distribution in the heating zone resulting from the reflection, absorption and transmission characteristics of the two joining partners is determined in a model-based manner as a function of the laser settings. Furthermore, the behavior of the foam and consolidation roller is mechanically characterized under process parameters and transferred to material models. The results of the investigations will then be combined and validated in a thermomechanical process model. By coupling the thermomechanical process model with a bond strength model, the influence of the process parameters on the bond quality between deposited tape layers and foam core will be explored. By generating a fundamental understanding, the basis for the fabrication of individually curved thermoplastic sandwich structures using laser-based TAFP is established.